Thin-film magnetic discs or media are widely used as data storage media for digital computers. The discs are typically formed by successively sputtering onto a rigid disc substrate, an underlayer, a magnetic layer, and a carbon overcoat which protects the magnetic layer against wear and reduces frictional forces between the disc and a read/write head.
A disc formed by the sputtering method just described typically contains uneven surface regions, due to surface irregularities in the substrate These irregularities, or asperities, may project above the surface of the disc several microinches. If the asperities were to make contact with a read/write head flying a few microinches over the surface of a spinning disc, the head could be ruined and/or the disc could crash. Therefore, it is necessary to subject the disc to a final surface treatment which removes surface asperities. It is also common to lubricate the disc, in a final surface treatment, with a thin film of a flurocarbon lubricant, to reduce frictional interactions between the head and the disc.
Heretofore, surface treatment of a magnetic medium to remove surface irregularities and debris on a magnetic disc has involved a two-step process which employs separate surface-treatment apparatuses In the first step, referred to herein as "buffing," or "tape-burnishing", the disc is positioned for rotation about a horizontal axis in a burnishing apparatus. This apparatus provides two pairs of movable, belt-like tapes which are brought into contact with the rotating disc, to remove surface debris and other loosely bound material by light abrasion The tapes may contain a lubricant for simultaneously applying lubricant to the surface.
In the second step, referred to herein as "waffle-burnishing," the disc is positioned for rotation about a vertical axis in a waffle-burnishing apparatus having a pair of waffle heads which are designed to fly over opposite-side surfaces of the spinning disc at a distance of 1-2 microinches, to remove asperities which may be formed integrally with the layers forming the disc. After the waffle-burnishing treatment, the disc is removed from the apparatus and may be further tested for read/write characteristics before packaging.
It can be appreciated that the surface treatment just described is inefficient, in that a technician must mount each disc in the tape-burnishing apparatus, wait for the tape-burnishing procedure to be completed, remove the disc from the apparatus, mount the disc on the waffle-burnishing apparatus, wait for completion of the waffle-burnishing procedure, then remove the disc for final packaging Another limitation of the prior-art method is that the waffle-burnishing procedure often leaves dislodged debris on the disc surfaces, particularly since the disc is disposed horizontally during the waffling procedure.